1. Field of the Invention
The present invention relates to a technology for detecting occurrence of write omission in a storage medium divided into a plurality of blocks.
2. Description of the Related Art
In a commonly used storage medium (for example, a disk) that is divided into a plurality of blocks, occurrence of a write omission prevents updating of data that is stored in each block and causes obsolete data to remain in the block. A cause of occurrence of the write omission is explained specifically with respect to FIG. 11. When a head carries out a write process to write updated data to the block that stores therein obsolete data, the head runs into dust particles etc. and data is not written to the block, thus causing obsolete data to remain in the block. The head running into the dust particles causes vibrations. Due to this, unreadable data (in other words, unrecovered read error) is written to adjacent blocks.
To take care of such a write omission, a write omission detecting method is carried out to detect the write omission. For example, a conventional write omission detecting method is disclosed in Japanese Patent Laid-open Application No. 2006-252530. In the conventional write omission detecting method, a history block, which stores therein updated data, is included for each block on the disk. When writing the updated data to the disk, a new updated status is stored in the history block and also stored in a memory of a central processing unit (CPU). Write omission is detected based on comparison of the updated status stored in the history block and the updated status stored in the memory.
However, in the conventional technology, because a process to detect the write omission is carried out after carrying out the write process, when carrying out the write process, detection of the write omission in all the blocks takes a significant time, which deteriorates the processing performance.